1. Field of the Invention
The present invention relates to the field of electronic timepieces, meaning timepieces having an electronic oscillator, such as a quartz crystal oscillator, that serves as the time standard for the timepiece. More specifically, the present invention relates to display technologies for electronic timepieces, where the display arrangement includes both analog and digital time indicators.
2. Description of the Related Art
To receive reasonable consumer acceptance, a modern electronic wristwatch or other body-worn timepiece must have certain basic features and capabilities. First, it must be fairly accurate--errors of less than 10 seconds per month are common in the industry. It must be convenient to operate and have a highly visible time display--preferably a display easily visible in both bright sunlight and low light conditions. The cost of acquiring and maintaining the timepiece must be reasonable. Finally, it must have a combination of features, displays, and overall appearance that are sufficiently innovative or otherwise appealing to make consumers want to wear it.
Watches that incorporate both a conventional, mechanically-driven, analog-type display and a digital, electrically-driven display have become popular as both consumers and manufacturers have realized that both types of displays have certain advantages in electronic body-worn timepiece applications. When electronic watches were new, consumers typically wanted to "advertise" that they possessed an electronic watch by having some sort of visible digital display. At the time, "solid state" watches were considered by many to be more reliable, more prestigious, and more desirable than their old-fashioned, mechanically-driven counterparts. Watch manufacturers thus sought to meet consumer demand by developing digital electro-optical displays that were suitable for electronic wristwatch applications.
However, the initial digital-display watches offered by manufacturers had many shortcomings. Wristwatches with digital light-emitting diode (LED) displays were bulky and consumed so much power that the display was ordinarily off, requiring inconvenient two-handed operation by the wearer to command the display to "turn on." Moreover, while LED displays were highly visible at night, they were very hard to read in bright sunlight. The earliest liquid crystal displays (LCD) used in electronic watches consumed far less power than LEDs, but these displays typically had an unacceptably short lifetime. The first LCDs also had contrast problems that limited users to fairly narrow viewing angles. Advances in electronics, display, and battery technology have resolved many of these problems, making current electro-optical displays much more practical for body-worn timepiece applications.
However, although currently available digital displays are far more serviceable for watch applications than were their predecessors, consumers' preferences have changed. As electronic watches became readily and cheaply available in the market, their "prestige" wore off. Consumers also came to realize that while a digital display was convenient in some respects, it was inconvenient in many others. Generally speaking, it is easier to tell the time by glancing at an analog clock face than by reading a relatively small set of numbers. Moreover, consumers are thought to prefer analog displays to quickly assess time intervals, i.e., how much time has elapsed since a specified time or how much time remains before a specified time. For example, if it is currently 2:25 and one has an appointment at 3:00, consumers may find it easier to determine from an analog display that the appointment is 35 minutes away.
For these reasons, electronic wristwatches that contain complimentary analog and digital displays have become popular. A number of these types of wristwatches actually do not contain analog components, but rather, utilize an electronic display that simulates an analog display. The following U.S. Patents all disclose dual electronic displays where the analog-like portion of the display (i.e., a radial display similar to a clock face that is intended to convey the time of day in hours and minutes) does not include a conventional, motor-driven hour hand and minute hand: U.S. Pat. No. 4,198,810, issued on Apr. 22, 1980 to Fahrenschon; U.S. Pat. No. 4,077,032, issued on Feb. 28, 1978 to Volkman; U.S. Pat. No. 4,095,405, issued on Jun. 20, 1978 to Tanaka; and U.S. Pat. No. 4,320,484, issued on Mar. 16, 1982, to Burdet.
On the other hand, U.S. Pat. No. 3,911,665, issued on Oct. 14, 1975 to van Berkum, discloses a wristwatch having complimentary mechanically-driven analog and electrically-driven digital displays. However, van Berkum's alphanumeric digital display is limited to the on-command display of the date. At the user's command, passing seconds can be electronically displayed via a "seconds marker," described as a single LED or a relatively small group of LEDs that flash at the rate of 1 Hz. U.S. Pat. No. 4,436,435, issued on Mar. 13, 1984 to Ushikoshi, discloses a wristwatch having complimentary analog and digital displays, where the digital display is located above (or in approximately the same plane) as the analog watch dial, thus allowing for a thin overall design. The wristwatch disclosed by Ushikoshi provides a conventional analog display that may or may not include a second hand, and a complimentary digital display that indicates hours and minutes in alphanumeric format. The digital display may or may not also include an alarm indicator and a flashing colon between the hours and minutes that indicates passing seconds. In Ushikoshi's wristwatch, both displays are driven by a single battery and a single time standard and timing circuit.
The present invention comprises a dual-display electronic wristwatch that incorporates a novel arrangement of the analog and digital displays, and utilizes separate batteries, time standards, and driving circuits for each display. Rather than displaying the same time-of-day information in two separate formats, or related time/date information, as disclosed in the above-described prior art, the present invention displays time-of-day information in analog format and passing seconds in alphanumeric format. Thus, the present invention is both a timepiece and a chronometric instrument, enabling the user to readily ascertain the both the time-of-day and the elapsed time between successive events with reasonable precision. Finally, the present invention provides a particularly unique and appealing appearance.